Rotor and motor

ABSTRACT

A rotor includes a field member arranged between a first core base of a first rotor core and a second core base of a second rotor core in the axial direction. When magnetized in the axial direction, the field member causes primary claw-shaped magnetic poles to function as primary magnetic poles and secondary claw-shaped magnetic poles to function as secondary magnetic poles. The field member is formed by placing a plurality of members one over another in the axial direction.

BACKGROUND

The present disclosure relates a rotor and a motor.

A rotor used in a motor disclosed in Japanese Laid-Open Utility ModelPublication H05-43749 is a rotor having a Lundell-type structure andincludes a pair of rotor cores each having a plurality of claw-shapedmagnetic poles in a circumferential direction and assembled with eachother. By arranging a field magnet as a disc magnet between the rotorcores, the respective claw-shaped magnetic poles are caused to functionas alternately different magnetic poles.

A Lundell-type rotor structure has an advantage of being able to easilyachieve multipolarity by a simple structure due to the formation of themagnetic poles on the claw-shaped magnetic poles by the disc magnetbetween the rotor cores.

In the Lundell-type rotor structure, the claw-shaped magnetic poles havea three-dimensional shape radially protruding outward from a core baseand axially extending from a radially outer end. Thus, unlike rotors ofgeneral technology in which a cross-sectional shape in a directionperpendicular to an axis is the same at all positions, Lundell-typerotors cannot easily adjust an output characteristic and the shape ofthe claw-shaped magnetic poles is changed for each targetcharacteristic. This leads to a cost increase.

Further, an output characteristic of the Lundell-type rotor structure isaffected by main magnetic flux generated from the disc magnet betweenthe rotor cores. Thus, it is desired that the shape of the rotor more bemade suitable for achieving a higher motor output.

Further, in the Lundell-type rotor, the number of components tends to belarge. Associated with this, there has been a problem that the number ofassembling steps increases.

SUMMARY

An objective of the present disclosure is to provide a rotor that easilyenables an output adjustment and a reduction in the number of componentswithout changing the shape thereof, and a motor including such a rotor.

In accordance with one aspect of the present disclosure, a rotor isprovided that includes a first rotor core, a second rotor core, and afield member. The first rotor core includes a substantially disk-shapedfirst core base and a plurality of primary claw-shaped magnetic polesformed at equal intervals on an outer peripheral part of the first corebase. The primary claw-shaped magnetic poles protrude radially outwardand extending in an axial direction. The second rotor core includes asubstantially disk-shaped second core base and a plurality of secondaryclaw-shaped magnetic poles formed at equal intervals on an outerperipheral part of the second core base. The secondary claw-shapedmagnetic poles protrude radially outward and extend in the axialdirection. Each secondary claw-shaped magnetic pole is arranged betweencorresponding primary claw-shaped magnetic poles. The field member isarranged between the first core base and the second core base in theaxial direction. When magnetized in the axial direction, the fieldmember causes the primary claw-shaped magnetic poles to function asprimary magnetic poles and the secondary claw-shaped magnetic poles tofunction as secondary magnetic poles. The field member is formed byplacing a plurality of members one over another in the axial direction.

According to this aspect, an output is easily adjusted without changingthe shape of the rotor by placing the members one over another in theaxial direction to form the field member.

In accordance with one form of the present disclosure, the field membercomprises of a plurality of permanent magnets.

According to this aspect, an output is easily adjusted without changingthe shape of the rotor by placing the permanent magnets one over anotherin the axial direction to form the field member.

In accordance with one form of the present disclosure, the field membercomprises a permanent magnet and a magnetic member.

According to this aspect, an output is easily adjusted without changingthe shape of the rotor by placing the permanent magnet and the magneticmember one over the other in the axial direction to form the fieldmember.

In accordance with one form of the present disclosure, the field memberis formed by arranging a magnetic member between a plurality ofpermanent magnets.

According to this aspect, an output is easily adjusted without changingthe shape of the rotor by arranging the magnetic member between thepermanent magnets and placing the permanent magnets and the magneticmember one over another in the axial direction to form the field member.

The present disclosure also provides a motor including the abovedescribed rotor.

According to this aspect, a motor is realized of which the output iseasily adjusted without changing the shape of the rotor.

In accordance with another aspect of the present disclosure, a rotor isprovided that includes a first rotor core, a second rotor core, and afield member. The first rotor core includes a substantially disk-shapedfirst core base and a plurality of primary claw-shaped magnetic polesformed at equal intervals on an outer peripheral part of the first corebase. The primary claw-shaped magnetic poles protrude radially outwardand extending in an axial direction. The second rotor core includes asubstantially disk-shaped second core base and a plurality of secondaryclaw-shaped magnetic poles formed at equal intervals on an outerperipheral part of the second core base. The secondary claw-shapedmagnetic poles protrude radially outward and extend in the axialdirection. Each secondary claw-shaped magnetic pole is arranged betweencorresponding primary claw-shaped magnetic poles. The field member isarranged between the first core base and the second core base in theaxial direction. When magnetized in the axial direction, the fieldmember causes the primary claw-shaped magnetic poles to function asprimary magnetic poles and the secondary claw-shaped, magnetic poles tofunction as secondary magnetic poles. A surface that is notperpendicular to the direction of magnetization is formed on at leastone of axial end surfaces of the field member.

According to this aspect, the surface area of contact surfaces of thefield member held in contact with the first core base and the secondcore base is increased in the field member arranged between the firstrotor core and the second rotor core. Thus, magnetic flux densities fromthe field member to the first core base and the second core base areincreased and a higher output of a motor is achieved.

In accordance with one form of the present disclosure, a tapered surfaceis formed on a part of the axial end surface of the field member.

According to this aspect, the surface area of the contact surfaces ofthe field member held in contact with the first core base and the secondcore base is increased and magnetic flux densities for the first corebase and the second core base are increased by forming the taperedsurface on at least the part of the axial end surface of the fieldmember. A higher output of a motor is achieved.

In accordance with one form of the present disclosure, a bellows-likecorrugated surface is formed on the axial end surface of the fieldmember.

According to this aspect, the surface area of the contact surfaces ofthe field member held in contact with the first core base and the secondcore base is increased by forming the bellows-like corrugated surface onthe axial end surface of the field member. Thus, magnetic flux densitiesfor the first core base and the second core base are increased and ahigher output of a motor is achieved.

In accordance with one form of the present disclosure, the axial endsurface of the field member is held in contact with a corresponding oneof a facing surface of the first core base and a facing surface of thesecond core base via a spacer that has a surface shape in conformitywith the shape of the axial end surface of the field member and isformed of a magnetic member.

According to this aspect, the spacer increases magnetic flux densitiesof the field member for the first core base and the second core basewithout changing the shapes of the first core base and the second corebase. Thus, a higher output of a motor is achieved.

In accordance with one form of the present disclosure, a motor includingthe above described rotor is provided.

According to this aspect, a high-output motor is realized withoutchanging the size of the rotor.

In accordance with another aspect of the present disclosure, a rotor isprovided that includes a first rotor core, a second rotor core, a fieldmember, and auxiliary magnets. The first rotor core includes asubstantially disk-shaped first core base and a plurality of primaryclaw-shaped magnetic poles formed at equal intervals on an outerperipheral part of the first core base. The primary claw-shaped magneticpoles protrude radially outward and extend in an axial direction. Thesecond rotor core includes a substantially disk-shaped second core baseand a plurality of secondary claw-shaped magnetic poles formed at equalintervals on an outer peripheral part of the second core base. Thesecondary claw-shaped magnetic poles protrude radially outward andextending in the axial direction. Each secondary claw-shaped magneticpole is arranged between corresponding primary claw-shaped magneticpoles. The field member is arranged between the first core base and thesecond core base in the axial direction. When magnetized in the axialdirection, the field member causes the primary claw-shaped magneticpoles to function as primary magnetic poles and the secondaryclaw-shaped magnetic poles to function as secondary magnetic poles. Eachof the auxiliary magnets is arranged in one of a clearance formed by theback surface of one of the claw-shaped magnetic pole and a clearancebetween one of the primary claw-shaped magnetic poles and thecorresponding one of the secondary claw-shaped magnetic poles in acircumferential direction. At least the auxiliary magnets or the fieldmember is formed integrally with at least one of the first rotor coreand the second rotor core.

According to this aspect, the auxiliary magnets arranged in at leasteither of the clearances formed by the back surfaces of the respectiveclaw-shaped magnetic poles or the clearances between the respectiveclaw-shaped magnetic poles in the circumferential direction are formedas an integral component with at least one of the first and second rotorcores. This can reduces the number of components as compared with aconfiguration as a comparative example in which the respective rotorcores, the field member and the auxiliary magnets are all separatebodies. This also leads to a smaller number of component assemblingsteps and, consequently, contributes to a reduction in componentassembling cost. Further, magnetic fluxes can be made difficult to leakfrom clearances of the rotor by the auxiliary magnets. Furthermore,according to this aspect, since the field member is formed as anintegral component with at least one of the first and second rotorcores, the number of components is reduced as compared with aconfiguration as a comparative example in which the respective rotorcores and the field member are all separate bodies. Further, the numberof component assembling steps is reduced, and hence, componentassembling cost is reduced.

In accordance with one form of the present disclosure, the auxiliarymagnets include primary back magnets arranged in the clearances formedby the back surfaces of the primary claw-shaped magnetic poles andsecondary back magnets arranged in the clearances formed by the backsurfaces of the secondary claw-shaped magnetic poles. The primary backmagnets are formed integrally with the first rotor core. The secondaryback magnets are formed integrally with the second rotor core.

According to this aspect, leakage magnetic fluxes from the clearancesformed by the back surfaces of the respective claw-shaped magnetic polesare suppressed by the respective back magnets and the number ofcomponents is reduced.

In accordance with one form of the present disclosure, the auxiliarymagnets are formed integrally with each rotor core and the field member.

According to this aspect, the rotor is composed of a smaller number ofcomponents since the respective rotor cores, the field member and theauxiliary magnets are formed as an integral component.

In accordance with one form of the present disclosure, the rotor coresare formed by powder magnetic cores.

According to this aspect, the respective rotor cores can be compressionmolded together with the auxiliary magnets or the field member since therespective rotor cores are formed by powder magnetic cores. Thiscontributes to simplification in manufacturing.

In accordance with one form of the present disclosure, a motor includingthe above described rotor is provided.

Another aspect of the present disclosure is directed to a rotormanufacturing method that includes: providing a first rotor coreincluding a substantially disk-shaped first core base and a plurality ofprimary claw-shaped magnetic poles formed at equal intervals on an outerperipheral part of the first core base, the primary claw-shaped magneticpoles protrude radially outward and extend in an axial direction;providing a second rotor core including a substantially disk-shapedsecond core base and a plurality of secondary claw-shaped magnetic polesformed at equal intervals on an outer peripheral part of the second corebase, the secondary claw-shaped magnetic poles protruding radiallyoutward and extending in the axial direction and each secondaryclaw-shaped magnetic pole being arranged between corresponding primaryclaw-shaped magnetic poles; providing a field member arranged betweenthe first core base and the second core base in the axial direction andcausing the primary claw-shaped magnetic poles to function as primarymagnetic poles and the secondary claw-shaped magnetic poles to functionas secondary magnetic poles by being magnetized in the axial direction;providing auxiliary magnets arranged in either one of clearances formedby the back surfaces of the respective claw-shaped magnetic poles andclearances between the primary claw-shaped magnetic poles and thesecondary claw-shaped magnetic poles in a circumferential direction; andforming at least either the auxiliary magnets or the field memberintegrally with at least either one of the first rotor core and thesecond rotor core.

According to this aspect, the auxiliary magnets arranged in at leasteither of the clearances formed by the back surfaces of the respectiveclaw-shaped magnetic poles and the clearances between the respectiveclaw-shaped magnetic poles in the circumferential direction are formedas an integral component with at least one of the first and second rotorcores. This reduces the number of components as compared with aconfiguration as a comparative example in which the respective rotorcores, the field member and the auxiliary magnets are all separatebodies. This can also lead to a smaller number of component assemblingsteps and, consequently, can contribute to a reduction in componentassembling cost. Further, magnetic fluxes can be made difficult to leakfrom clearances of the rotor by the auxiliary magnets. Furthermore,according to this aspect, since the field member is formed as anintegral component with at least one of the first and second rotorcores, the number of components is reduced as compared with aconfiguration as a comparative example in which the respective rotorcores and the field member are all separate bodies. This can also leadto a smaller number of component assembling steps and, consequently, cancontribute to a reduction in component assembling cost.

Other aspects and advantages of the discloser will become apparent fromthe following description, taken in conjunction with the accompanyingdrawings, illustrating by way of example the principles of thedisclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present disclosure that are believed to be novel areset forth with particularity in the appended claims. The disclosure,together with objects and advantages thereof, may best be understood byreference to the following description of the presently preferredembodiments together with the accompanying drawings in which:

FIG. 1 is a cross-sectional view of a motor of a first embodiment;

FIG. 2 is a cross-sectional view in a direction perpendicular to an axisof the motor in FIG. 1;

FIG. 3 is a perspective view of the rotor in FIG. 1;

FIG. 4 is a cross-sectional view of the rotor in FIG. 3;

FIG. 5 is an exploded perspective view of the rotor in FIG. 3;

FIG. 6 is a cross-sectional view showing a rotor of a modification;

FIG. 7 is a cross-sectional view showing a rotor of anothermodification;

FIG. 8 is a cross-sectional view of a motor of a second embodiment;

FIG. 9 is a cross-sectional view in a direction perpendicular to an axisof the motor in FIG. 8;

FIG. 10 is a perspective view of the rotor in FIG. 8;

FIG. 11 is a cross-sectional view of the rotor in FIG. 10;

FIG. 12 is an exploded perspective view of the rotor in FIG. 10;

FIG. 13 is a perspective view, partly cut away, showing a field memberof a third embodiment;

FIG. 14 is a cross-sectional view showing a rotor including the fieldmember of FIG. 13;

FIG. 15 is a cross-sectional view showing a rotor of a fourthembodiment;

FIG. 16 is a cross-sectional view of a motor of a fifth embodiment;

FIG. 17 is a plan view of the motor of FIG. 16;

FIG. 18 is a perspective view of a rotor of FIG. 16;

FIG. 19 is a cross-sectional view of the rotor of FIG. 18;

FIG. 20 is an exploded perspective view of the rotor of FIG. 18;

FIGS. 21( a) to 21(d) are diagrams showing a manufacturing method forthe rotor of FIG. 18;

FIGS. 22( a) to 22(d) are diagrams showing a manufacturing method for arotor of a modification;

FIG. 23 is a perspective view of a rotor of a sixth embodiment;

FIGS. 24( a) to 24(d) are diagrams showing a manufacturing method forthe rotor of FIG. 23; and

FIG. 25 is a perspective view of a rotor of a modification.

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

A first embodiment of the present disclosure will now be described withreference to the drawings.

As shown in FIG. 1, a motor case 2 of a motor 1 includes a cylindrical,housing 3 in the form of a tube with a closed end and a front end plate4 for closing an opening at a front side of the cylindrical housing 3,i.e. located on a left side in FIG. 1. A circuit storage box 5 storing apower supply circuit such as a circuit board is mounted on a rear sideof the cylindrical housing 3, i.e. on an end part located on a rightside in FIG. 1. A stator 6 is fixed to the inner peripheral surface ofthe cylindrical housing 3

As shown in FIG. 2, the stator 6 includes an armature core 7 with aplurality of teeth 7 a extending radially inward and a segment conductor(SC) coil 8 wound on the teeth 7 a of the armature core 7. A rotor 11 ofthe motor 1 includes a rotary shaft 12 and is arranged inside the stator6. The rotary shaft 12 is a metal shaft made of nonmagnetic material androtationally supported by a bearing 13 supported on a bottom part 3 a ofthe cylindrical housing 3 and a bearing 14 supported on the front endplate 4.

(Rotor 11)

As shown in FIGS. 3, 4 and 5, the rotor 11 includes a first rotor core20, a second rotor core 30 and an annular field member 40 as a fieldmember and a field magnet. The annular field member 40 will be describedwith reference to FIGS. 4 and 5.

(First Rotor Core 20)

As shown in FIGS. 3, 4 and 5, the first rotor core 20 includes asubstantially disk-shaped first core base 21 and a plurality of primaryclaw-shaped magnetic poles 22 formed at equal intervals on an outerperipheral part of the first core base 21. The primary claw-shapedmagnetic poles 22 protrude radially outward and are bent to extend inthe axial direction. In the first embodiment, there are five primaryclaw-shaped magnetic poles 22. Circumferential end surfaces 22 a, 22 bof the primary claw-shaped magnetic pole 22 are flat surfaces extendingin a radial direction and not inclined with respect to the radialdirection when viewed in the axial direction. The primary claw-shapedmagnetic pole 22 has a sectoral cross-section in a directionperpendicular to the axis. The angle of each primary claw-shapedmagnetic pole 22 in the circumferential direction, i.e. the anglebetween the circumferential end surfaces 22 a and 22 b is set to besmaller than the angle of the clearance between the primary claw-shapedmagnetic poles 22 adjacent in the circumferential direction.

(Second Rotor Core 30)

As shown in FIGS. 3, 4 and 5, the second rotor core 30 has the sameshape as the first rotor core 20. The second rotor core 30 includes asubstantially disk-shaped second core base 31 and a plurality ofsecondary claw-shaped magnetic poles 32 formed at equal intervals on anouter peripheral part of the second core base 31. The secondaryclaw-shaped magnetic poles 32 protrude radially outward and are bent toextend in the axial direction. Circumferential end surfaces 32 a, 32 bof the secondary claw-shaped magnetic pole 32 are flat surfacesextending in the radial direction and not inclined with respect to theradial direction when viewed in the axial direction. The secondaryclaw-shaped magnetic pole 32 has a sectoral cross-section in a directionperpendicular to the axis. The angle of each secondary claw-shapedmagnetic pole 32 in the circumferential direction, i.e. the anglebetween the circumferential end surfaces 32 a and 32 b is set to besmaller than the angle of the clearance between the secondaryclaw-shaped magnetic poles 32 adjacent in the circumferential direction.

Each secondary claw-shaped magnetic pole 32 of the second rotor core 30is arranged between corresponding primary claw-shaped magnetic poles 22.At this time, the second rotor core 30 is assembled with the first rotorcore 20 such that the annular field member 40 shown in FIG. 4 isarranged and sandwiched between the first core base 21 and the secondcore base 31 in the axial direction.

Specifically, the first core base 21 includes an inward facing surface21 a facing the second core base 31, the second core base 31 includes aninward facing surface 31 a facing the first core base 21, and theannular field member 40 is sandwiched between the inward facing surface21 a of the first core base 21 and the inward facing surface 31 a of thesecond core base 31.

At this time, one circumferential end surface 22 a of the primaryclaw-shaped magnetic pole 22 and the other circumferential end surface32 b of the secondary claw-shaped magnetic pole 32 are formed to beparallel to each other in the axial direction. Thus, the clearancebetween one circumferential end surface 22 a of the primary claw-shapedmagnetic pole 22 and the other circumferential end surface 32 b of thesecondary claw-shaped magnetic pole 32 is substantially straight in theaxial direction. Similarly, the other circumferential end surface 22 bof the primary claw-shaped magnetic pole 22 and one circumferential endsurface 32 a of the secondary claw-shaped magnetic pole 32 are formed tobe parallel to each other in the axial direction. Thus, the clearancebetween the other circumferential end surface 22 b of the primaryclaw-shaped magnetic pole 22 and one circumferential end surface 32 a ofthe secondary claw-shaped magnetic pole 32 is substantially straight inthe axial direction.

(Annular Field Member 40)

As shown in FIGS. 4 and 5, the annular field member 40 is sandwichedbetween the first rotor core 20 and the second rotor core 30 and formedby placing a plurality of unit permanent magnets 41 one over another. Inthis embodiment, there are two unit permanent magnets 41. The outerdiameter of the unit permanent magnets 41 is set to be equal to that ofthe first core base 21 and that of the second core base 31. Thethickness of the unit permanent magnets 41 is set at a predeterminedthickness.

In the first embodiment, the number of the unit permanent magnets 41used in the annular field member 40 and placed one over the other isdetermined by the axial length of the primary claw-shaped magnetic poles22 and that of the secondary claw-shaped magnetic poles 32.

That is, when the annular field member 40 is sandwiched between thefirst rotor core 20 and the second rotor core 30, the number of the unitpermanent magnets 41 is selected such that tip end surfaces 22 c of theprimary claw-shaped magnetic poles 22 and an outward facing surface 31 bof the second core base 31 are flush with each other and tip endsurfaces 32 c of the secondary claw-shaped magnetic poles 32 and anoutward facing surface 21 b of the first core base 21 are flush witheach other.

In the first embodiment, the annular field member 40 is formed byplacing the two unit permanent magnets 41 one over the other and the tipend surfaces 22 c of the primary claw-shaped magnetic poles 22 and theoutward facing surface 31 b of the second core base 31 are flush witheach other and the tip end surfaces 32 c of the secondary claw-shapedmagnetic poles 32 and the outward facing surface 21 b of the first corebase 21 are flush with each other.

That is, the annular field member 40 is formed by placing the two unitpermanent magnets 41 one over the other and the axial length of therotor 11 is set to be substantially equal to that of the armature core7.

In other words, the axial length of the rotor 11 can be adjusted bychanging the number of the unit permanent magnets 41 to adjust thethickness of the annular field member 40

The two unit permanent magnets 41 constituting the annular field member40 are placed one over the other so as to have the same direction ofmagnetization. In FIG. 4, arrows shown by solid line in the unitpermanent magnets 41 indicate the direction of magnetization, i.e. adirection from a south pole to a north pole of the field member 40.

The annular field member 40 is magnetized in the axial direction tocause the primary claw-shaped magnetic poles 22 to function as primarymagnetic poles and the secondary claw-shaped magnetic poles 32 tofunction as secondary magnetic poles. In the first embodiment, theprimary magnetic poles are north poles and the secondary magnetic polesare south poles.

Accordingly, the rotor 11 of the first embodiment is a rotor having aLundell-type structure using the annular field member 40. In the rotor11, the primary claw-shaped magnetic poles 22 serving as north poles andthe secondary claw-shaped magnetic poles 32 serving as south poles arealternately arranged in the circumferential direction and there are tenmagnetic poles, i.e. there are five pole pairs. Since the number of thepole pairs is an odd number greater than or equal to three, theclaw-shaped magnetic poles having the same polarity are not at oppositepositions spaced apart by 180° in the circumferential direction in eachrotor core. Thus, such an arrangement of the claw-shaped magnetic polesis stable against magnetic vibration.

In the motor 1 configured as described above, a magnetic field forrotating the rotor 11 is generated in the stator 6, and the rotor 11 isrotated when a three-phase drive current is supplied to the segmentconductor (SC) coil 8 via the power supply circuit in the circuitstorage box 5.

Operation of the first embodiment configured as described above will nowbe described.

The thickness of the annular field member 40 is adjusted only byproviding the unit permanent magnets 41 and changing the number of theunit permanent magnets 41 placed one over the other. Even if the axiallength of the rotor 11 differs, the first embodiment can be applied tovarious rotors having different axial lengths by changing the number ofthe unit permanent magnets 41.

Further, an output characteristic of the motor 1 can be appropriatelychanged and adjusted without changing the size of the motor 1, forexample, by changing the two unit permanent magnets 41 to unit permanentmagnets having mutually different magnetic flux densities.

The first embodiment has the following advantages.

(1) According to the first embodiment, the annular field member 40sandwiched between the first rotor core 20 and the second rotor core 30is formed by placing a plurality of, e.g. two unit permanent magnets 41one over another. The axial length of the rotor 11 is adjusted and madesuitable by changing the number of the unit permanent magnets 41 toadjust the thickness of the annular field member 40.

Thus, the first embodiment can be applied to rotors 11 of variousdifferent sizes only by providing one type of permanent magnetcomponents called unit permanent magnets 41. As a result, only one typeof permanent magnet components is necessary, wherefore components can beeasily managed and made uniform and suitable.

(2) According to the first embodiment, the annular field member 40 isformed by placing a plurality of unit permanent magnets 41 one overanother. Specifically, the thickness, i.e. axial length of the annularfield member 40, which is a permanent magnet, can be increased by aplurality of unit permanent magnets 41.

Thus, in the first embodiment, it is not necessary to use one thickpermanent magnet, which is difficult to produce and costly, as theannular field member. Therefore, a cost reduction can be realizedwithout reducing the output of the motor 1.

(3) Further, according to the first embodiment, the outputcharacteristic of the motor 1 can be appropriately changed and adjustedwithout changing the size of the motor 1 by forming the annular fieldmember 40 by two unit permanent magnets 41 having mutually differentmagnetic flux densities.

The first embodiment may be modified as follows.

In the first embodiment, the annular field member 40 is formed by twounit permanent magnets 41. However, the embodiment is not limited to twounit permanent magnets 41, but three or more unit permanent magnets maybe placed one over another in conformity with the size of a rotor.

In the first embodiment, the respective unit permanent magnets 41 havethe same thickness, i.e., have one thickness. However, the axial lengthof the rotor can be accurately and finely, adjusted by providing aplurality of types of unit permanent magnets having mutually differentthicknesses and appropriately combining and placing these types of unitpermanent magnets one over another.

In the first embodiment, the annular field member 40 is formed by twounit permanent magnets 41. Without being limited to this, the annularfield member 40 may be formed by arranging one magnetic member 42 madeof the same magnetic material as the first rotor core 20 and the secondrotor core 30 on each of opposite sides of one unit permanent magnet 41as shown in FIG. 6. In this case, the annular field member 40 may beformed by making the magnetic members 42 of a magnetic materialdifferent from the magnetic material of the first rotor core 20 and thesecond rotor core 30, e.g. a magnetic material having a high magneticpermeability. The rotor 11 may be embodied by improving the output ofthe motor 1 in this way.

In the first embodiment, the annular field member 40 is formed by twounit permanent magnets 41. Without being limited to this, the annularfield member 40 may be formed by providing two unit permanent magnets 41and arranging a magnetic member 43 made of the same magnetic material asthe first rotor core 20 and the second rotor core 30 between the twounit permanent magnets 41 as shown in FIG. 7. Also in this case, theannular field member 40 may be similarly formed by making the magneticmember 43 of a magnetic material different from the magnetic material ofthe first rotor core 20 and the second rotor core 30, e.g. a magneticmaterial having a high magnetic permeability. The rotor 11 may beembodied by improving the output of the motor 1 in this way.

Second Embodiment

A second embodiment of the present disclosure will now described withreference to the drawings.

As shown in FIG. 8, a motor case 2 of a motor 1 includes a cylindricalhousing 3 in the form of a tube with a closed end and a front end plate4 for closing an opening at a front side of the cylindrical housing 3,i.e. located on a left side in FIG. 8. A circuit storage box 5 storing apower supply circuit such as a circuit board is mounted on a rear sideof the cylindrical housing 3, i.e. on an end part located on a rightside in FIG. 8. A stator 6 is fixed to the inner peripheral surface ofthe cylindrical housing 3.

As shown in FIG. 9, the stator 6 includes an armature core 7 with aplurality of teeth 7 a extending radially inward and a segment conductor(SC) coil 8 wound on the teeth 7 a of the armature core 7. A rotor 11 ofthe motor 1 includes a rotary shaft 12 and is arranged inside the stator5. The rotary shaft 12 is a metal shaft made of nonmagnetic material androtationally supported by a bearing 13 supported on a bottom part 3 a ofthe cylindrical housing 3 and a bearing 14 supported on the front endplate 4.

(Rotor 11)

As shown in FIGS. 10, 11 and 12, the rotor 11 includes a first rotorcore 20, a second rotor core 30 and a field member 40, which is a fieldmagnet. The field member 40 is illustrated in FIGS. 11 and 12.

(First Rotor Core 20)

As shown in FIGS. 10, 11 and 12, the first rotor core 20 includes asubstantially disk-shaped first core base 21 and a plurality of primaryclaw-shaped magnetic poles 22 formed at equal intervals on an outerperipheral part of the first core base 21. The primary claw-shapedmagnetic poles 22 protrude radially outward and are bent to extend inthe axial direction. In the second embodiment, there are five primaryclaw-shaped magnetic poles 22. Circumferential end surfaces 22 a, 22 bof the primary claw-shaped magnetic pole 22 are flat surfaces extendingin a radial direction and not inclined with respect to the radialdirection when viewed in the axial direction. The primary claw-shapedmagnetic pole 22 has a sectoral cross-section in a directionperpendicular to the axis. The angle of each primary claw-shapedmagnetic pole 22 in the circumferential direction, i.e. the anglebetween the circumferential end surfaces 22 a and 22 b is set to besmaller than the angle of the clearance between the primary claw-shapedmagnetic poles 22 adjacent in the circumferential direction.

A shaft hole 21 c through which the rotary shaft 12 is inserted andfixed is formed at a center position of the substantially disk-shapedfirst core base 21. The first core base 21 includes an inward facingsurface 21 a facing the second rotor core 30 and the inward facingsurface 21 a is recessed. Specifically, the inward facing surface 21 ais recessed as a truncated conical surface, of which the diameterdecreases toward the shaft hole 21 c. In the second embodiment, theinward facing surface 21 a recessed as the truncated conical surfacedefines a first fitting recess 23.

(Second Rotor Core 30)

As shown in FIGS. 10, 11 and 12, the second rotor core 30 has the sameshape as the first rotor core 20 and includes a substantiallydisk-shaped second core base 31 and a plurality of secondary claw-shapedmagnetic poles 32 formed at equal intervals on an outer peripheral partof the second core base 31. The secondary claw-shaped magnetic poles 32protrude radially outward and are bent to extend in the axial direction.In the second embodiment, there are five secondary claw-shaped magneticpoles 32. Circumferential end surfaces 32 a, 32 b of the secondaryclaw-shaped magnetic pole 32 are flat surfaces extending in the radialdirection and not inclined with respect to the radial direction whenviewed in the axial direction. The secondary claw-shaped magnetic pole32 has a sectoral cross-section in a direction perpendicular to theaxis. The angle of each secondary claw-shaped magnetic pole 32 in thecircumferential direction, i.e. the angle between the circumferentialend surfaces 32 a and 32 b is set to be smaller than the angle of theclearance between the secondary claw-shaped magnetic poles 32 adjacentin the circumferential direction.

A shaft hole 31 c through which the rotary shaft 12 is inserted andfixed is formed at a center position of the substantially disk-shapedsecond core base 31. The second core base 31 facing the first rotor core20 includes an inward facing surface 31 a facing the first rotor core 20and the inward facing surface 31 a is recessed. Specifically, the inwardfacing surface 31 a is recessed as a truncated conical surface, of whichthe diameter decreases toward the shaft hole 31 c. In the secondembodiment, the inward facing surface 31 a recessed as the truncatedconical surface defines a second fitting recess 33.

Each secondary claw-shaped magnetic pole 32 of the second rotor core 30is arranged between corresponding primary claw-shaped magnetic poles 22.The second rotor core 30 is assembled with the first rotor core 20 suchthat the field member 40 shown in FIG. 11 is arranged and sandwichedbetween the first core base 21 and the second core base 31 in the axialdirection.

Specifically, the field member 40 is sandwiched between the firstfitting recess 23 of the first core base 21 and the second fittingrecess 33 of the second core base 31

One circumferential end surface 22 a of the primary claw-shaped magneticpole 22 and the other circumferential end surface 32 b of the secondaryclaw-shaped magnetic pole 32 are arranged to face each other and extendin parallel in the axial direction. Thus, the clearance between onecircumferential end surface 22 a of the primary claw-shaped magneticpole 22 and the other circumferential end surface 32 b of the secondaryclaw-shaped magnetic pole 32 is formed to be substantially straight inthe axial direction. Similarly, the other circumferential end surface 22b of the primary claw-shaped magnetic pole 22 and one circumferentialend surface 32 a of the secondary claw-shaped magnetic pole 32 arearranged to face each other and extend in parallel in the axialdirection. Thus, the clearance between the other circumferential endsurface 22 b of the primary claw-shaped magnetic pole 22 and onecircumferential end surface 32 a of the secondary claw-shaped magneticpole 32 is formed to be substantially straight in the axial direction.

(Field Member 40)

As shown in FIGS. 11 and 12, the field member 40 sandwiched between thefirst rotor core 20 and the second rotor core 30 is a permanent magnetthat is cylindrically formed. The outer diameter of the field member 40is set to be equal to that of the first core base 21 and that of thesecond core base 31, A shaft hole 40 a through which the rotary shaft 12is inserted and fixed is formed at a center position of the cylindricalfield member 40.

A first end surface 40 b of the field member 40 facing the first rotorcore 20 protrudes. Specifically, the first end surface 40 b protrudes asa truncated conical tapered surface, of which the diameter decreasestoward the shaft hole 40 a. In the second embodiment, the first endsurface 40 b protruding as the truncated conical shape defines a firstfitting protrusion 44. Thus, the first end surface 40 b of the fieldmember 40 facing the first rotor core 20 is formed not to beperpendicular to the axial direction, thereby increasing the surfacearea of the first end surface 40 b.

A second end surface 40 c of the field member 40 facing the second rotorcore 30 protrudes. Specifically, the second end surface 40 c protrudesas a truncated conical tapered surface, of which the diameter decreasestoward the shaft hole 40 a. In the second embodiment, the second endsurface 40 c protruding as the truncated conical shape defines a secondfitting protrusion 45. Thus, the second end surface 40 c of the fieldmember 40 facing the second rotor core 30 is formed not to beperpendicular to the axial direction, thereby increasing the surfacearea of the second end surface 40 c.

When the field member 40 is sandwiched between the first rotor core 20and the second rotor core 30, the first fitting recess 23 is held inclose contact with the first fitting protrusion 44 and the secondfitting recess 33 is held in close contact with the second fittingprotrusion 45. Further, the field member 40 is formed such that tip endsurfaces 22 c of the primary claw-shaped magnetic poles 22 and anoutward facing surface 31 b of the second core base 31 are flush witheach other, and tip end surfaces 32 c of the secondary claw-shapedmagnetic poles 32 and an outward facing surface 21 b of the first corebase 21 are flush with each other.

The field member 40 is magnetized in a direction of magnetization shownby a broken-line arrow in the field member 40 in FIG. 11, i.e. in adirection from a south pole to a north pole. The field member 40 ismagnetized in the axial direction to cause the primary claw-shapedmagnetic poles 22 to function as primary magnetic poles and thesecondary claw-shaped magnetic poles 32 to function as secondarymagnetic poles. In the second embodiment, the primary magnetic poles arenorth poles and the secondary magnetic poles are south poles.

Accordingly, the rotor 11 of the second embodiment is a rotor having aLundell-type structure using the field member 40. In the rotor 11, theprimary claw-shaped magnetic poles 22 serving as north poles and thesecondary claw-shaped magnetic poles 32 serving as south poles arealternately arranged in the circumferential direction and there are tenmagnetic poles, i.e., there are five pole pairs. Since the number of thepole pairs is an odd number greater than or equal to three, theclaw-shaped magnetic poles having the same polarity are not at oppositepositions spaced apart by 180° in the circumferential direction in eachrotor core. Thus, such an arrangement of the claw-shaped magnetic polesis stable against magnetic vibration.

When the field member 40 is sandwiched between the first rotor core 20and the second rotor core 30, the surface area of the first end surface40 b of the field member 40 facing the first rotor core 20 and that ofthe second end surface 40 c facing the second rotor core 30 areincreased by forming the first end surface 40 b and the second endsurface 40 c into the tapered surfaces. Thus, magnetic flux densitiesfor the first core base 21 and the second core base 31 can be increased.

In the motor 1 configured as described above, a magnetic field forrotating the rotor 11 is generated in the stator 6 and the rotor 11 isrotated when a three-phase drive current is supplied to the segmentconductor (SC) coil 8 via the power supply circuit in the circuitstorage box 5

Operation of the second embodiment configured as described above willnow be described.

In the rotor 11 having a Lundell-type structure, the first fittingprotrusion 44 having a truncated conical shape is formed to protrude onthe first end surface 40 b of the field member 40 sandwiched between thefirst rotor core 20 and the second rotor core 30, and the second fittingprotrusion 45 having a truncated conical shape is formed to protrude onthe second end surface 40 c of the field member 40. The first fittingrecess 23 having a truncated conical shape is provided by recessing theinward facing surface 21 a of the first rotor core 20 and the secondfitting recess 33 having a truncated conical shape is provided byrecessing the inward facing surface 31 a of the second rotor core 30.

When the field member 40 is sandwiched between the first rotor core 20and the second rotor core 30, the first fitting recess 23 of the firstrotor core 20 is fitted to the first fitting protrusion 44 of the fieldmember 40 and the second fitting recess 33 of the second rotor core 30is fitted to the second fitting protrusion 45 of the field member 40.

At this time, a part of the inward facing surface 21 a of the firstrotor core 20 held in contact with the first end surface 40 b of thefield member 40 is not a surface perpendicular to the axial direction,but a surface inclined with respect to the axial direction since thefirst fitting protrusion 44 and the first fitting recess 23 have thetruncated conical shapes.

Accordingly, the surface area of the contact surface of the firstfitting protrusion 44 of the first end surface 40 b with the firstfitting recess 23 of the inward facing surface 21 a increases, magneticresistance is reduced, and a magnetic flux density from the field member40 to the first core base 21 can be increased.

Similarly, a part of the inward facing surface 31 a the second rotorcore 30 held in contact with the second end surface 40 c of the fieldmember 40 is not a surface perpendicular to the axial direction, but asurface inclined with respect to the axial direction since the secondfitting protrusion 45 and the second fitting recess 33 have thetruncated conical shapes.

Accordingly, the surface area of the contact surface of the secondfitting protrusion 45 of the second end surface 40 c with the secondfitting recess 33 of the inward facing surface 31 a increases, magneticresistance is reduced, and a magnetic flux density from the second corebase 31 to the field member 40 can be increased.

The second embodiment has the following advantages.

(4) According to the second embodiment, the first fitting recess 23 isformed as a truncated conical recess on the first core base 21 of thefirst rotor core 20 and the first fitting protrusion 44 is formed as atruncated conical protrusion on the first end surface 40 b of the fieldmember 40.

Further, the second fitting recess 33 is formed as a truncated conicalrecess on the second core base 31 of the second rotor core 30 and thesecond fitting protrusion 45 is formed as a truncated conical protrusionon the second end surface 40 c of the field member 40

Magnetic resistance is reduced by increasing the surface area of thecontact surface of the field member 40 with the first core base 21 andthat of the contact surface of the field member 40 with the second corebase 31.

Thus, magnetic flux densities for the first core base 21 and the secondcore base 31 can be increased, and the output of the motor 1 can beincreased.

(5) Further, according to the second embodiment, the output of the motor1 can be easily adjusted without changing the overall shape of the rotor11 by changing the depth (axial dimension) of the first fitting recess23 and that of the second fitting recess 33 and changing the axiallength of the first fitting protrusion 44 and that of the second fittingprotrusion 45 in accordance with the former changes.

Third Embodiment

Next, a third embodiment of the present disclosure will be described.The third embodiment is characterized by the shape of a field member 40and, in conformity with this shape, characterized by inward facingsurfaces 21 a, 31 a of a first core base 21 and a second core base 31.In the following description, characteristic parts different from thesecond embodiment are described in detail and other common parts areomitted for the illustrative purposes.

As shown in FIG. 13, the field member 40 sandwiched between the firstcore base 21 and the second core base 31 is formed such that a first endsurface 40 b facing the first core base 21 is a bellows-like corrugatedsurface extending radially outward, i.e. a cross-section of the firstend surface 40 b in a direction perpendicular to an axis has asinusoidal shape. Thus, the first end surface 40 b of the field member40 facing the first core base 21 is a surface not perpendicular to theaxial direction and the surface area of the first end surface 40 bincreases.

Similarly, the field member 40 is formed such that a second end surface40 c is a bellows-like corrugated surface extending radially outward,i.e. a cross-section of the second end surface 40 c in a directionperpendicular to the axis has a sinusoidal shape. Thus, the second endsurface 40 c of the field member 40 facing the second core base 31 is asurface not perpendicular to the axial direction and the surface area ofthe second end surface 40 c increases.

On the other hand, as shown in FIG. 14, the first core base 21 includesthe inward facing surface 21 a and is formed such that the inward facingsurface 21 a is a bellows-like corrugated surface extending radiallyoutward, i.e. an axial cross-section of the inward facing surface 21 ahas a sinusoidal shape. Further, the field member 40 is formed such thatthe first end surface 40 b is a bellows-like corrugated surfaceextending radially outward, i.e. an axial cross-section of the first endsurface 40 b has a sinusoidal shape. The inward facing surface 21 a ofthe first core base 21 is fitted to the first end surface 40 b of thefield member 40. Thus, the inward facing surface 21 a of the first corebase 21 is a surface not perpendicular to the axial direction and thesurface area thereof increases.

Similarly, as shown in FIG. 14, the second core base 31 includes theinward facing surface 31 a and is formed such that the inward facingsurface 31 a is a bellows-like corrugated surface extending radiallyoutward, i.e. an axial cross-section of the inward facing surface 31 ahas a sinusoidal shape. Further, the field member 40 is formed such thatthe second end surface 40 c is a bellows-like corrugated surfaceextending radially outward, i.e. an axial cross-section of the secondend surface 40 c has a sinusoidal shape. The inward facing surface 31 aof the second core base 31 is fitted to the second end surface 40 c ofthe field member 40. Thus, the inward facing surface 31 a of the secondcore base 31 is a surface not perpendicular to the axial direction andthe surface area thereof increases.

This increases the surface area of a surface of the field member 40 heldin contact with the first core base 21 and that of a surface of thefield member 40 held in contact with the second core base 31 and reducesmagnetic resistance when the field member 40 is sandwiched between thefirst rotor core 20 and the second rotor core 30.

Therefore, the third embodiment has advantages similar to those of thesecond embodiment.

Fourth Embodiment

Next, a fourth embodiment of the present disclosure will be described.The fourth embodiment is characterized by the shape of a field member 40as in the third embodiment and, in conformity with this shape, ischaracterized by inward facing surfaces 21 a, 31 a of a first core base21 and a second core base 31. In the following description,characteristic parts different from the second embodiment are describedin detail and other common parts are omitted for the illustrativepurposes.

As shown in FIG. 15, the inward facing surface 21 a of the first corebase 21 and the inward facing surface 31 a of the second core base 31are flat surface perpendicular to the axial direction. A first spacerS1, which is a magnetic member, is provided between the inward facingsurface 21 a and the field member 40, and a second spacer S2, which is amagnetic member, is provided between the inward facing surface 31 a andthe field member 40.

A surface S1 b of the first spacer S1 facing the inward facing surface21 a is formed as a flat surface. A surface S1 a of the first spacer S1facing the field member 40 is formed as a truncated conical recessedsurface in conformity with the shape of a first fitting protrusion 44 ofthe field member 40, i.e. the shape of a first end surface 40 b. In thefourth embodiment, the surface S1 a of the first spacer S1 recessed tohave a truncated conical shape defines a first fitting recess 23.

Accordingly, the first end surface 40 b of the field member 40 facingthe first spacer S1, i.e., located on the side corresponding to thefirst core base 21, is a surface not perpendicular to the axialdirection and the surface area thereof increases.

A surface S2 b of the second spacer S2 facing the inward facing surface31 a is formed as a flat surface. A surface S2 a of the second spacer S2facing the field member 40 is formed as a truncated conical recessedsurface in conformity with the shape of a second fitting protrusion 45of the field member 40, i.e., the shape of a second end surface 40 c. Inthe fourth embodiment, the surface S2 a of the second spacer S2 recessedto have a truncated conical shape defines a second fitting recess 33

Accordingly, the second end surface 40 c of the field member 40 facingthe second spacer S2, i.e. located on the side corresponding to thesecond core base 31 is a surface not perpendicular to the axialdirection and the surface area thereof increases.

That is, when the field member 40 is sandwiched between the first rotorcore 20 and the second rotor core 30 via the first spacer S1 and thesecond spacer S2, the surface area of a surface of the field member 40held in contact with the first spacer S1 and that of a surface of thefield member 40 held in contact with the second spacer S2 increase andthe magnetic resistance is reduced.

Thus, in addition to the advantages of the second embodiment the fourthembodiment increases magnetic flux densities for the first core base 21and the second core base 31 and increases the output of the motor 1without changing the shapes of the first rotor core 20 and the secondrotor core 30.

The above embodiments may be modified as follows.

In the second embodiment, the opposite end surfaces 40 b, 40 c of thefield member 40 are entirely formed as the protrusions having thetruncated conical shapes. In conformity with these truncated conicalshapes, the entire inward facing surface 21 a of the first core base 21and the entire inward facing surface 31 a of the second core base 31 areformed as the recesses having the truncated conical shapes. Withoutbeing limited to this, the second embodiment may be so modified that apart of the first end surface 40 b of the field member 40 and a part ofthe second end surface 40 c of the field member 40 are formed asprotrusions having truncated conical shapes. In conformity with thesetruncated conical shapes, a part of the inward facing surface 21 a ofthe first core base 21 and a part of the inward facing surface 31 a ofthe second core base 31 are formed as recesses having truncated conicalshapes.

In the second embodiment, the opposite end surfaces 40 b, 40 c of thefield member 40 are formed as the protrusions having the truncatedconical shapes. In conformity with these truncated conical shapes, theinward facing surfaces 21 a, 31 a of the first core base 21 and thesecond core base 31 are formed as the recesses having the truncatedconical shapes. Without being limited to this, the second embodiment maybe so modified that the opposite end surfaces 40 b, 40 c of the fieldmember 40 are formed as protrusions having truncated pyramidal shapes.In conformity with these truncated pyramidal shapes, the inward facingsurface 21 a of the first core base 21 and the inward facing surface 31a of the second core base 31 are formed as recesses having truncatedpyramidal shapes.

The second embodiment may also be so modified that partial surfaces ofthe truncated pyramidal shapes are curved surfaces.

In the third embodiment, the opposite end surfaces 40 b, 40 c of thefield member 40 are formed to have the bellows-like shapes extendingradially outward, i.e., the axial cross-sections of the opposite endsurfaces 40 b, 40 c are formed to have the sinusoidal shapes. Inconformity with these shapes, the inward facing surface 21 a of thefirst core base 21 and the inward facing surface 31 a of the second corebase 21 are formed to have the bellows-like shapes.

Without being limited to this, the third embodiment may be so modifiedthat the opposite end surfaces 40 b, 40 c of the field member 40 areformed to have sawtooth-like shapes extending radially outward. Inconformity with these shapes, the inward facing surface 21 a of thefirst core base 21 and the inward facing surface 31 a of the second corebase 31 are formed to have sawtooth-like shapes.

The third embodiment may also be so embodied that sawtooth-like surfacesare formed on parts of the opposite end surfaces 40 b, 40 c of the fieldmember 40. In conformity with these sawtooth-like shapes, sawtooth-likesurfaces are formed on a part of the inward facing surface 21 a of thefirst core base 21 and a part of the inward facing surface 31 a of thesecond core base 31.

In the third embodiment, the opposite end surfaces 40 b, 40 c of thefield member 40 are formed to have the bellows-like shapes extendingradially outward. In conformity with these shapes, the inward facingsurface 21 a of the first core base 21 and the inward facing surface 31a of the second core base 31 are formed to have the bellows-like shapes.

Without being limited to this, the third embodiment may be so modifiedthat the opposite end surfaces. 40 b, 40 c of the field member 40 areformed as bellows-like or sawtooth-like surfaces circling around in thecircumferential direction in conformity with these bellows-like orsawtooth-like surfaces, the inward facing surface 21 a of the first corebase 21 and the inward facing surface 31 a of the second core base 31are formed as bellows-like or sawtooth-like surfaces circling around inthe circumferential direction.

Fifth Embodiment

A fifth embodiment of the present disclosure will now be described withreference to the drawings.

As shown in FIGS. 16 and 17, a motor case 2 of a motor 1 includes acylindrical housing 3 in the form of a tube with a closed end and afront end plate 4 for closing an opening at a front side of thecylindrical housing 3, i.e. located on a left side in FIG. 16. A circuitstorage box storing a power supply circuit such as a circuit, board ismounted on a rear side of the cylindrical housing 3, i.e., on an endpart located on a right, side in FIG. 16. A stator 6 is fixed to theinner peripheral surface of the cylindrical housing 3. The stator 6includes an armature core 7 with a plurality of teeth 7 a extendingradially inward and a segment conductor (SC) coil 8 wound on the teeth 7a of the armature core 7. A rotor 11 of the motor 1 includes a rotaryshaft 12 and is arranged inside the stator 6. The rotary shaft 12 is acylindrical metal shaft made of magnetic material and rotationallysupported by a bearing 13 supported on a bottom part 3 a of thecylindrical housing 3 and a bearing 14 supported on the front end plate4.

As shown in FIGS. 18, 19 and 20, the rotor 11 includes the rotary shaft12, a first rotor core 20, a second rotor core 30, an annular fieldmember 40 as a field magnet, primary back magnets 46 and secondary backmagnets 47 as auxiliary magnets.

The first rotor core 20 includes a substantially disk-shaped first corebase 21. A shaft hole 21 c into which the rotary shaft 12 is inserted isformed to extend through a central part of the first core base 21 in theaxial direction. The rotary shaft 12 is press-fitted and fixed into theshaft hole 21 c. This enables the first rotor core 20 and the rotaryshaft 12 to integrally rotate.

A plurality of primary claw-shaped magnetic poles 22 are so formed atequal intervals on an outer peripheral part of the first core base 21 asto protrude radially outward and extend in the axial direction. In thefifth embodiment, there are five primary claw-shaped magnetic poles 22.Circumferential end surfaces 22 a, 22 b of the primary claw-shapedmagnetic pole 22 are flat surfaces extending in a radial direction andnot inclined with respect to the radial direction when viewed in theaxial direction. The primary claw-shaped magnetic pole 22 has a sectoralcross-section in a direction perpendicular to the axis. The angle ofeach primary claw-shaped magnetic pole 22 in the circumferentialdirection, i.e. the angle between the circumferential end surfaces 22 aand 22 b is set to be smaller than the angle of the clearance betweenthe primary claw-shaped magnetic poles 22 adjacent in thecircumferential direction.

The primary back magnet 46 is provided on a back surface 22 e, i.e. on aradially inner surface of each primary claw-shaped magnetic pole 22. Theprimary back magnet 46 is formed integrally with each primaryclaw-shaped magnetic pole 22 of the first rotor core 20 by insertmolding. That is, as shown in FIG. 20, the first rotor core 20 and therespective primary back magnets 46 are formed as an integral component.As shown in FIG. 19, the primary back magnet 46 is held in close contactwith the back surface 22 e of the primary claw-shaped magnetic pole 22in the radial direction and held in close contact with a radiallyextending portion 22 d of the primary claw-shaped magnetic pole 22, i.e.a part radially extending from the first core base 21 in the axialdirection by being formed integrally with the primary claw-shapedmagnetic pole 22. This primary back magnet 46 is formed such that across-section thereof in a direction perpendicular to the axis issectoral and opposite circumferential end surfaces thereof arerespectively flat surfaces flush with the circumferential end surfaces22 a, 22 b of the primary claw-shaped magnetic pole 22. An axial tip endsurface 46 a of the primary back magnet 46, i.e., an end surface of theprimary back magnet 46 located at a side opposite to the radiallyextending portion 22 d is formed to be flush with a tip end surface 22 cof the primary claw-shaped magnetic pole 22.

As shown in FIGS. 19 and 20, the second rotor core 30 has the same shapeas the first rotor core 20. A shaft hole 31 c into which the rotaryshaft 12 is inserted is formed in a central part of a substantiallydisk-shaped second core base 31. The rotary shaft 12 is press-fitted andfixed into the shaft hole 31 c. This enables the second rotor core 30and the rotary shaft 12 to integrally rotate.

A plurality of secondary claw-shaped magnetic poles 32 are so formed atequal intervals on an outer peripheral part of the second core base 31as to protrude radially outward and extend in the axial direction.Circumferential end surfaces 32 a, 32 b of the secondary claw-shapedmagnetic pole 32 are radially extending flat surfaces. The secondaryclaw-shaped magnetic pole 32 has a sectoral cross-section in a directionperpendicular to the axis. The angle of each secondary claw-shapedmagnetic pole 32 in the circumferential direction, i.e., the anglebetween the circumferential end surfaces 32 a and 32 b is set to besmaller than the angle of the clearance between the secondaryclaw-shaped magnetic poles 32 adjacent in the circumferential direction.

The secondary back magnet 47 is provided on a back surface 32 e i.e., ona radially inner surface of each secondary claw-shaped magnetic pole 32.The secondary back magnet 47 is formed integrally with each secondaryclaw-shaped magnetic pole 32 of the second rotor core 30 by insertmolding. That is, as shown in FIG. 20, the second rotor core 30 and therespective secondary back magnets 47 are formed as an integralcomponent. As shown in FIG. 19, the secondary back magnet 47 is held inclose contact with the back surface 32 e of the secondary claw-shapedmagnetic pole 32 in the radial direction and held in close contact witha radially extending portion 32 d of the secondary claw-shaped magneticpole 32, i.e., a part radially extending from the second core base 31 inthe axial direction by being formed integrally with the secondaryclaw-shaped magnetic pole 32. This secondary back magnet 47 is formedsuch that a cross-section thereof in the direction perpendicular to theaxis is sectoral and opposite circumferential end surfaces thereof arerespectively flat surfaces flush with the circumferential end surfaces32 a, 32 b of the secondary claw-shaped magnetic pole 32. An axial tipend surface 47 a of the secondary back magnet 47. i.e. an end surface ofthe secondary back magnet 47 located at a side opposite to the radiallyextending portion 32 d is formed to be flush with a tip end surface 32 cof the secondary claw-shaped magnetic pole 32.

The second rotor core 30 is assembled with the first rotor core 20 suchthat each secondary claw-shaped magnetic pole 32 is arranged betweencorresponding primary claw-shaped magnetic poles 22. Specifically, theprimary claw-shaped magnetic poles 22 and the secondary claw-shapedmagnetic poles 32 are so formed that one circumferential end surface 22a of the primary claw-shaped magnetic pole 22 and the othercircumferential end surface 32 b of the secondary claw-shaped magneticpole 32 are parallel to each other in the axial direction. This causesthe clearance between the respective circumferential end surfaces 22 a,32 b to be substantially straight in the axial direction. Similarly, theprimary claw-shaped magnetic poles 22 and the secondary claw-shapedmagnetic poles 32 are so formed that the other circumferential endsurface 22 b of the primary claw-shaped magnetic pole 22 and onecircumferential end surface 32 a of the secondary claw-shaped magneticpole 32 are parallel to each other in the axial direction. This causesthe clearance between the respective circumferential end surfaces 22 b,32 a to be substantially straight in the axial direction.

A radially inner surface 46 b of the primary back magnet 46 integrallyformed to the primary claw-shaped magnetic pole 22 is held in contactwith an outer peripheral surface 31 d of the second core base 31 in aradial direction. Similarly, a radially inner surface 46 b of thesecondary back magnet 47 integrally formed to the secondary claw-shapedmagnetic pole 32 is held in contact with an outer peripheral surface 21d of the first core base 21 in a radial direction. That is, the primaryback magnet 46 is located between the second core base 31 and theprimary claw-shaped magnetic pole 22 in the radial direction, and thesecondary back magnet 47 is located between the first core base 21 andthe secondary claw-shaped magnetic pole 32 in the radial direction. Thetip end surface 22 c of the primary claw-shaped magnetic pole 22 and theaxial tip end surface 46 a of the primary back magnet 46 are formed tobe flush with an outward facing surface 31 b, which is an axial outerend surface of the second core base 31. Similarly, the tip end surface32 c of the secondary claw-shaped magnetic pole 32 and the axial tip endsurface 47 a of the secondary back magnet 47 are formed to be flush withan outward facing surface 21 b, which is an axial outer end surface ofthe first core base 21.

The field member 40, which is an annular magnet, is arranged andsandwiched between the first core base 21 and the second core base 31 inthe axial direction. The field member 40 is in the form of a circularring and the rotary shaft 12 extends through a central part thereof. Thefield member 40 is held in close contact with an inward facing surface21 a, which is an axial inner end surface of the first core base 21, andan inward facing surface 31 a, which is an axial inner end surface ofthe second core base 31, respectively. The inward facing surface 21 a ofthe first core base 21, the inward facing surface 31 a of the secondcore base 31 and opposite axial end surfaces of the field member 40 areflat surfaces perpendicular to an axis of the rotary shaft 12. The outerperipheral surface of the field member 40 is held in contact with theradially inner surfaces 46 b of the primary back magnets 46 and theradially inner surfaces 47 b of the secondary back magnets 47 in radialdirections. That is, the primary back magnet 46 is located between thefield member 40 and the primary claw-shaped magnetic pole 22 in theradial direction and the secondary back magnet 47 is located between thefield member 40 and the secondary claw-shaped magnetic pole 32 in theradial direction.

The field member 40 is magnetized in the axial direction to cause theprimary claw-shaped magnetic poles 22 to function as primary magneticpoles and the secondary claw-shaped magnetic poles 32 to function assecondary magnetic poles. In this embodiment, the primary magnetic polesare north poles and the secondary magnetic poles are south poles.Accordingly, the rotor 11 of this embodiment is a rotor having aLundell-type structure using the annular field member 40 as an annularmagnet. In the rotor 11, the primary claw-shaped magnetic poles 22serving as north poles and the secondary claw-shaped magnetic poles 32serving as south poles are alternately arranged in the circumferentialdirection and there are ten magnetic poles, i.e., there are five polepairs. Since the number of the pole pairs is an odd number greater thanor equal to three, the claw-shaped magnetic poles having the samepolarity are not at opposite positions spaced apart by 180° in thecircumferential direction in each rotor core. Thus, such an arrangementof the claw-shaped magnetic poles is stable against magnetic vibration.

The primary back magnet 46 is magnetized in the radial direction suchthat a surface held in contact with the primary claw-shaped magneticpole 22, i.e. a radially outer surface serves as a north pole having thesame polarity as the primary claw-shaped magnetic pole 22 and a surfaceheld in contact with the second core base 31, i.e. a radially innersurface serves as a south pole having the same polarity as the secondcore base 31. Similarly, the secondary back magnet 47 is magnetized inthe radial direction such that a surface held in contact with thesecondary claw-shaped magnetic pole 32, i.e., a radially outer surfaceserves as a south pole having the same polarity as the secondaryclaw-shaped magnetic pole 32 and a surface held in contact with thefirst core base 21, i.e. a radially inner surface serves as a north polehaving the same polarity as the first core base 21. The magnetic flux ofthe primary back magnet 46 flows into the primary claw-shaped magneticpole 22 and the magnetic flux of the secondary back magnet 47 flows intothe secondary claw-shaped magnetic pole 32. These magnetic fluxescontribute to the generation of torque of the rotor 11.

In the motor 1 configured as described above, a magnetic field forrotating the rotor 11 is generated in the stator 6 and the rotor 11 isrotated when a three-phase drive current is supplied to the segmentconductor (SC) coil 3 via the power supply circuit in the circuitstorage box 5.

Next, operation of the fifth embodiment will now be described.

The primary back magnet 46 is located in the clearance in the radialdirection between the back surface 22 e of the primary claw-shapedmagnetic pole 22 and the second core base 31. The secondary back magnet47 is located in the clearance in the radial direction between the backsurface 32 e of the secondary claw-shaped magnetic pole 32 and the firstcore base 21. In this way, leakage magnetic flux from the clearance ofthe back surface 22 e of the primary claw-shaped magnetic pole 22 andthat from the clearance of the back surface 32 e of the secondaryclaw-shaped magnetic pole 32 are respectively suppressed by the primaryback magnet 46 and the secondary back magnet 47.

The primary back magnets 46 are formed integrally with the first rotorcore 20 and the secondary back magnets 47 are formed integrally with thesecond rotor core 30. That is, the first rotor core 20 and the primaryback magnets 46 are formed as an integral component, and the secondrotor core 30 and the secondary back magnets 47 are formed as anotherintegral component. In this way, in the fifth embodiment, the number ofcomponents is reduced as compared with a configuration as a comparativeexample in which the first rotor core 20, the second rotor core 30, thefield member 40, the primary back magnets 46 and the secondary backmagnets 47 are all separate bodies. As a result, the number of componentassembling steps is reduced and, consequently, the fifth embodimentcontributes to the reduction in component assembling cost.

Next, a method for manufacturing the rotor 11 of the fifth embodimentwill be described. A method for manufacturing an integral moldingproduct of the first rotor core 20 and the primary back magnets 46 ismainly described below in accordance with FIGS. 21( a) to 21(d). FIGS.21( a) to 21(d) planarly show cross-sections bent at a predeterminedangle to pass through circumferential centers of two primary claw-shapedmagnetic poles 22.

FIG. 21( a) shows a first mold 51 as a recessed mold for producing theintegral molding product of the first rotor core 20 and the primary backmagnets 46.

First, as shown in FIG. 21( b), the already formed first rotor core 20is arranged in the first mold 51.

Subsequently, as shown in FIG. 21( c), a second mold 52 as a protrudingmold is arranged above the first mold 51. Subsequently, after cavitiesformed between the second mold 52 and the back surfaces 22 e of theprimary claw-shaped magnetic poles 22 are filled with a mixture ofmagnetic powder and resin material, the primary back magnets 46 made ofbonded magnet are formed by solidifying the mixture. In this way, theprimary back magnets 46 are formed integrally with the first rotor core20 so as to be held in close contact with and fixed to the back surfaces22 e and the radially extending portions 22 d of the primary claw-shapedmagnetic poles 22.

Subsequently, magnetizers 53 for generating a magnetic field magnetizethe primary back magnets 46. By this magnetization, the primary backmagnets 46 are magnetized in the radial direction so that the radiallyouter surfaces, i.e. the surfaces facing the primary claw-shapedmagnetic poles 22 serve as north poles and the radially inner surfacesserve as south poles. Thereafter, the finished product of the integralmolding product of the first rotor core 20 and the primary back magnets46 shown in FIG. 21( d) is removed from the first mold 51 and the secondmold 52.

An integral molding product of the second rotor core 30 and thesecondary back magnets 47 is also produced in a procedure similar to theabove. A direction of magnetization of the secondary back magnets 47 isopposite to that of the primary back magnets 46, i.e. the radially outersurfaces are magnetized to be south poles and the radially innersurfaces are magnetized to be north poles.

Subsequently, the integral molding product composed of the first rotorcore 20 and the primary back magnets 46 and the integral molding productcomposed of the second rotor core 30 and the secondary back magnets 47are assembled to sandwich the field member 40 therebetween and arrangeeach secondary claw-shaped magnetic pole 32 between correspondingprimary claw-shaped magnetic poles 22 in the circumferential direction.Thereafter, the rotary shaft 12 is press-fitted and fixed into the shaftholes 21 c of the first core base 21 and the shaft hole 31 c of thesecond core base 31, whereby the rotor 11 shown in FIGS. 18 and 19 iscompleted.

Next, a characteristic advantage of the fifth embodiment will bedescribed.

(6) The rotor 11 includes the primary back magnets 46 arranged in theclearances formed by the back surfaces 22 e of the primary claw-shapedmagnetic poles 22 and the secondary back magnets 47 arranged in theclearances formed by the back surfaces 32 e of the secondary claw-shapedmagnetic poles 32. The primary back magnets 46 are formed integrallywith the first rotor core 20 and the secondary back magnets 47 areformed integrally with the second rotor core 30. That is, the firstrotor core 20 and the primary back magnets 46 are formed as an integralcomponent and the second rotor core 30 and the secondary back magnets 47are formed as a different integral component. Thus, the number ofcomponents is suppressed in the fifth embodiment as compared with aconfiguration as a comparative example in which the first rotor core 20,the second rotor core 30, the field member 40, the primary back magnets46 and the secondary back magnets 47 are all separate bodies. As aresult, the number of component assembling steps is suppressed and,consequently, the fifth embodiment contributes to a reduction incomponent assembling cost. Further, the primary back magnets 46 suppressleakage magnetic fluxes from the clearances formed by the back surfaces22 e of the primary claw-shaped magnetic poles 22 and the secondary backmagnets 47 suppress leakage magnetic fluxes from the clearances formedby the back surfaces 32 e of the secondary claw-shaped magnetic poles32.

The fifth embodiment of the present disclosure may be modified asfollows.

In the fifth embodiment, the integral molding product composed of thefirst rotor core 20 and the primary back magnets 46 is formed by insertmolding using the first rotor core 20 and the second rotor core 30 asinserts. However, besides this, the first rotor core 20 and the primaryback magnets 46 may be integrally formed by two-color molding.

An example of a manufacturing method by two-color molding will bedescribed in accordance with FIGS. 22( a) to 22(d). Similar to FIGS. 21(a) to 21(d), FIGS. 22( a) to 22(d) also show cross-sections bent at apredetermined angle to pass through circumferential centers of twoprimary claw-shaped magnetic poles 22.

FIG. 22( a) shows a first mold 61 as a recessed mold for producing theintegral molding product of the first rotor core 20 and the primary backmagnets 46 by two-color molding.

First, as shown in FIG. 22( b), a cylindrical second mold 62 is arrangedin the first mold 61. Then, cavities formed between the inner peripheralsurface of the second mold 62 and a cylindrical central extendingportion 61 a of the first mold 61 is filled with hard magnetic powder,which will form the primary back magnets 46.

Subsequently, the second mold 62 is removed and the space between theinner peripheral surface of the first mold 61 and the primary backmagnets 46 is filled with soft magnetic powder, which will form thefirst rotor core 20 as shown in FIG. 22( c). Thereafter, a third mold 63in the form of a flat plate is arranged on top of the first mold 61 andthe soft magnetic powder and the hard magnetic powder are compressed bythe third mold 63 (compression molding). Thereafter, the integralmolding product of the first rotor core 20 and the primary back magnets46 is formed by heating the soft magnetic powder and the hard magneticpowder. That is, the first rotor core 20 is formed by a powder magneticcore.

Subsequently, magnetizers 53 for generating a magnetic field magnetizethe primary back magnets 46. By this magnetization, the primary backmagnets 46 are magnetized in the radial direction so that the radiallyouter surfaces, i.e., the surfaces facing the primary claw-shapedmagnetic poles 22 serve as north poles and the radially inner surfacesserve as south poles. Thereafter, the finished, product of the integralmolding product of the first rotor core 20 and the primary back magnets46 shown in FIG. 22( d) is removed from the first mold 61 and the thirdmold 63.

An integral molding product of the second rotor core 30 and thesecondary back magnets 47 is also produced in a procedure similar to theabove. A direction of magnetization of the secondary hack magnets 47 isopposite to that of the primary back magnets 46, i.e. the radially outersurfaces are magnetized to be south poles and the radially innersurfaces are magnetized to be north poles.

According to this manufacturing method, the first rotor core 20 and thesecond rotor core 30 can be compression molded together with the primaryback magnets 46 and the secondary back magnets 47 since the first rotorcore 20 and the second rotor core 30 are formed by the powder magneticcores. This simplifies a manufacturing process. Since the first rotorcore 20 and the primary back magnets 46 are integrally formed bytwo-color molding, the integrity of the first rotor core 20 and theprimary back magnets 46 is improved.

In the rotor 11 of the fifth embodiment, the primary back magnets 46 andthe first rotor core 20 are integrally formed. However, the rotor 11 isnot particularly limited to this configuration. For example, the rotor11 may be so configured that the first rotor core 20, the second rotorcore 30 and the field member 40 are integrally formed. In this case, therotor 11 may be so configured that the primary back magnets 46 and thesecondary back magnets 47 are fixed to the primary claw-shaped magneticpoles 22 such as by adhesion. Further, the primary back magnets 46 andthe secondary back magnets 47 may be omitted and the rotor 11 may becomposed of the first rotor core 20, the second rotor core 30 and thefield member 40. Further, the rotor 11 may be so configured that thefirst rotor core 20, the second rotor core 30 and the field member 40are integrally formed. Further, the rotor 11 may be so configured thatthe field member 40 is formed integrally with either one of the firstrotor core 20 and the second rotor core 30.

According to such a configuration, the field member 40 and at least oneof the first rotor core 20 and the second rotor core 30 are formed as anintegral component. Thus, the number of components is suppressed ascompared with a configuration as a comparative example in which all theconstituent components of the rotor 11 are separate bodies. Therefore,the number of component assembling steps can be suppressed and,consequently, component assembling cost can be reduced.

Sixth Embodiment

A rotor 11A of a sixth embodiment shown in FIG. 23 is configured suchthat all of a first rotor core 20, a second rotor core 30, a fieldmember 40, primary back magnets 46 and secondary back magnets 47 areintegrally formed. Components similar to those of the fifth embodimentare denoted by the same reference signs and not described in detail.

As shown in FIGS. 23 and 24( d), in the rotor 11A of the sixthembodiment, a radially inner surface 46 b of each primary back magnet 46is radially separated from the outer peripheral surface of the fieldmember 40 and an outer peripheral surface 31 d of a second core base 31.Similarly, a radially inner surface 47 b of each secondary back magnet47 is radially separated from the outer peripheral surface of the fieldmember 40 and an outer peripheral surface 21 d of a first core base 21.The outer peripheral surface 21 d of the first core base 21, the outerperipheral surface 31 d of the second core base 31 and the outerperipheral surf ace of the field member 40 are formed to have the samediameter.

Next, a method for manufacturing the rotor 11A of the sixth embodimentwill be described.

FIG. 24( a) shows a first mold 71 as a recessed mold for manufacturingan integral molding product composed of the first rotor core 20, thesecond rotor core 30, the field member 40, the primary back magnets 46and the secondary back magnets 47 by two-color molding.

First, as shown in FIG. 24( b), the first mold 71 is filled in apredetermined fashion with soft magnetic powder, which will form thefirst rotor core 20 and the second rotor core 30, hard magnetic powder,which will form the field member 40, the primary back magnets 46 and thesecondary back magnets 47, and disappearing powder P made of sublimatesuch as naphthalene.

Next, a second mold 72 in the form of a flat plate is arranged on top ofthe first mold 71 and the powders filling the first mold 71 arecompressed by the second mold 72 (compression molding). Thereafter, anintegral component composed of the first rotor core 20, the second rotorcore 30, the field member 40 and the primary back magnets 46 and thesecondary back magnets 47 is formed as shown in FIG. 24( c) by heatingthe soft magnetic powder, the hard magnetic powder and the disappearingpowder P. That is, the first rotor core 20 and the second rotor core 30are formed by powder magnetic cores. The disappearing powder P, e.g.naphthalene is sublimated by this heating, and radial clearances areformed between the radially inner surfaces 46 b of the primary backmagnets 46 and the field member 40 and the second core base 31 and otherradial clearances are formed between the radially inner surfaces 47 b ofthe secondary back magnets 47 and the field member 40 and the first corebase 21 by this sublimation.

Subsequently, magnetizers 53 for generating a magnetic field magnetizethe primary back magnets 46, the secondary back magnets 47 and the fieldmember 40. Magnetic fluxes from the magnetizers 53 arranged radiallyoutwardly of the primary claw-shaped magnetic poles 22 pass the primaryclaw-shared magnetic poles 22 and the primary back magnets 46 in theradial direction, propagate radially inward through the first core base21 from there, and pass the field member 40 in the axial direction.Similarly, magnetic fluxes from the magnetizers 53 arranged radiallyoutwardly of the secondary claw-shaped magnetic poles 32, pass thesecondary claw-shaped magnetic poles 32 and the secondary back magnets47 in the radial direction, propagate radially inward through the secondcore base 31 from there, and pass the field member 40 in the axialdirection. In this way, the primary back magnets 46 and the secondaryback magnets 47 are magnetized to have mutually different polarities andthe field member 40 is magnetized in the axial direction.

Thereafter, an integral molding product shown in FIG. 24( d) is removedfrom the first and second molds 71, 72 and the rotary shaft 12 ispress-fitted and fixed into the shaft hole 21 c of the first core base21 and the shaft hole 31 c of the second core base 31, whereby the rotor11A shown in FIG. 23 is completed.

An advantage similar to the advantage (6) of the fifth embodiment isobtained also by the sixth embodiment. In addition, the primary backmagnets 46, the secondary back magnets 47, the first rotor core 20, thesecond rotor core 30 and the field member 40 are formed as an integralcomponent since they are integrally formed. As a result, the rotor 11Aof the sixth embodiment is composed of a smaller number of components.Since the first rotor core 20 and the second rotor 30 are formed by thepowder magnetic cores in the sixth embodiment, the first rotor core 20and the second rotor core 30 can be compression molded together with thefield member 40, the primary back magnets 46 and the secondary backmagnets 47. This simplifies a manufacturing process. Since the firstrotor core 20, the second rotor core 30, the field member 40, theprimary back magnets 46 and the secondary back magnets 47 are integrallyformed by two-color molding, the integrity of the rotor 11A is improved.

The fifth and sixth embodiments of the present disclosure may bemodified as follows.

In the sixth embodiment, sublimate such as naphthalene is used as thedisappearing powder P. However, besides this, meltage or water-solublematter such as sodium chloride may be used to replace the disappearingpowder P.

In the fifth and sixth embodiments, primary interpole magnets 48 andsecondary interpole magnets 49 as shown in FIG. 25 may be provided asauxiliary magnets. FIG. 25 shows an example in which the primaryinterpole magnets 48 and the secondary interpole magnets 49 are providedin the rotor 11 of the fifth embodiment.

The primary interpole magnets 48 and the secondary interpole magnets 49are arranged between the primary claw-shaped magnetic poles 22 and thesecondary claw-shaped magnetic poles 32 in the circumferentialdirection. Specifically, the primary interpole magnet 48 is locatedbetween a flat surface formed by one circumferential end surface 22 a ofthe primary claw-shaped magnetic pole 22 and the circumferential endsurface of the primary back magnet 46 and a flat surface formed by theother circumferential end surface 32 b of the secondary claw-shapedmagnetic pole 32 and the circumferential end surface of the secondaryback magnet 47. The secondary interpole magnet 49 has the same shape asthe primary interpole magnet 48 and is located between a flat surfaceformed by the other circumferential end surface 22 b of the primaryclaw-shaped magnetic pole 22 and the circumferential end surface of theprimary back magnet 46 and a flat surface formed by one circumferentialend surface 32 a of the secondary claw-shaped magnetic pole 32 and thecircumferential end surface of the secondary back magnet 47. The primaryinterpole magnets 48 and the secondary interpole magnets 49 aremagnetized in the circumferential direction so that parts having thesame polarities respectively face the primary claw-shaped magnetic poles22 and the secondary claw-shaped magnetic poles 32, i.e. surfaces facingthe primary claw-shaped magnetic poles 22 serve as north poles andsurfaces facing the secondary claw-shaped magnetic poles 32 serve assouth poles.

In such a configuration, the primary interpole magnets 48 and thesecondary interpole magnets 49 are respectively formed integrally withthe first rotor core 20 or the second rotor core 30 or both of theprimary interpole magnets 48 and the secondary interpole magnets 49 areformed integrally with either one of the first rotor core 20 and thesecond rotor core 30. By doing so, the number of components is reducedas compared with a configuration as a comparative example in which allthe constituent components of the rotor 11 are separate bodies. As aresult, the number of component assembling steps is reduced and,consequently, this embodiment contributes to a reduction in thecomponent assembling cost. Although the primary back magnets 46 areformed integrally with the first rotor core 20 and the secondary backmagnets 47 are formed integrally with the second rotor core 30 in thefifth embodiment, only the primary interpole magnets 48 and thesecondary interpole magnets 49 may be formed integrally with the firstrotor core 20 and the second rotor core 30 in a modification. With theprimary back magnets 46 and the secondary back magnets 47 omitted, therotor 11A may be so configured that the primary interpole magnets 48 andthe secondary interpole magnets 49 are respectively formed integrallywith the first rotor core 20 and the second rotor core 30.

In the configuration in which the primary interpole magnets 48 and thesecondary interpole magnets 49 are provided in the rotor 11A of thesixth embodiment, only one constituent component of the rotor 11A exceptthe rotary shaft 12 can be achieved if all the constituent components ofthe rotor 11A except the rotary shaft 12, i.e. the first rotor core 20,the second rotor core 30, the field member 40, the primary back magnets46, the secondary back magnets 47, the primary interpole magnets 48 andthe secondary interpole magnets 49 are integrally formed. Thisconfiguration is more effective.

The number of poles of the stator 6 the number of poles of the rotor 11,the numbers of, e.g., the primary claw-shaped magnetic poles 22 and thesecondary claw-shaped magnetic poles 32 in each of the above embodimentsmay be appropriately changed according to the configuration.

In each of the above embodiments, the shapes of the first rotor core 20and the second rotor core 30 may be appropriately changed according tothe configuration.

In the fifth and sixth embodiments, the field member 40 as an annularmagnet is magnetized to cause the primary claw-shaped magnetic poles 22to function as north poles and the secondary claw-shaped magnetic poles32 to function as south poles. However, the magnetic poles of theannular field member 40 may be reversed and the annular field member 40may cause the primary claw-shaped magnetic poles 22 to function as southpoles and the secondary claw-shaped magnetic poles 32 to function asnorth poles.

In the fifth and sixth embodiments, one annular field member 40 is usedas a field magnet. However, the annular field member 40 may be soconfigured that a plurality of divided parts of a permanent magnet arearranged around the rotary shaft 12 between the first core base 21 andthe second core base 31 in the axial direction.

Although how to wind the winding on the teeth of the stator 6 is notparticularly mentioned in the fifth and sixth embodiments, concentratedwinding or distributed winding may be used.

1. A rotor, comprising: a first rotor core including a substantially disk-shaped first core base and a plurality of primary claw-shaped magnetic poles formed at equal intervals on an outer peripheral part of the first core base, the primary claw-shaped magnetic poles protruding radially outward and extending in an axial direction; a second rotor core including a substantially disk-shaped second core base and a plurality of secondary claw-shaped magnetic poles formed at equal intervals on an outer peripheral part of the second core base, the secondary claw-shaped magnetic poles protruding radially outward and extending in the axial direction and each secondary claw-shaped magnetic pole being arranged between corresponding primary claw-shaped magnetic poles; and a field member arranged between the first core base and the second core base in the axial direction, wherein, when magnetized in the axial direction, the field member causes the primary claw-shaped magnetic poles to function as primary magnetic poles and the secondary claw-shaped magnetic poles to function as secondary magnetic poles, wherein the field member is formed by placing a plurality of members one over another in the axial direction.
 2. The rotor according to claim 1, wherein the field member comprises of a plurality of permanent magnets.
 3. The rotor according to claim 1, wherein the field member comprises a permanent magnet and a magnetic member.
 4. The rotor according to claim 1, wherein the field member is formed by arranging a magnetic member between a plurality of permanent magnets.
 5. A motor comprising the rotor according to claim
 1. 6. A rotor, comprising: a first rotor core including a substantially disk-shaped first core base and a plurality of primary claw-shaped magnetic poles formed at equal intervals on an outer peripheral part of the first core base, the primary claw-shaped magnetic poles protruding radially outward and extending in an axial direction; a second rotor core including a substantially disk-shaped second core base and a plurality of secondary claw-shaped magnetic poles formed at equal intervals on an outer peripheral part of the second core base, the secondary claw-shaped magnetic poles protruding radially outward and extending in the axial direction and each secondary claw-shaped magnetic pole being arranged between corresponding primary claw-shaped magnetic poles; and a field member arranged between the first core base and the second core base in the axial direction, wherein, when magnetized in the axial direction, the field member causes the primary claw-shaped magnetic poles to function as primary magnetic poles and the secondary claw-shaped magnetic poles to function as secondary magnetic poles, wherein a surface that is not perpendicular to the direction of magnetization is formed on at least one of axial end surfaces of the field member.
 7. The rotor according to claim 6, wherein a tapered surface is formed on a part of the axial end surface of the field member.
 8. The rotor according to claim 6, wherein a bellows-like corrugated surface is formed on the axial end surface of the field member.
 9. The rotor according to claim 6, wherein the axial end surface of the field member is held in contact with a corresponding one of a facing surface of the first core base and a facing surface of the second core base via a spacer that has a surface shape in conformity with the shape of the axial end surface of the field member and is formed of a magnetic member.
 10. A motor, comprising the rotor according to claim
 6. 11. A rotor, comprising: a first rotor core including a substantially disk-shaped first core base and a plurality of primary claw-shaped magnetic poles formed at equal intervals on an outer peripheral part of the first core base, the primary claw-shaped magnetic poles protruding radially outward and extending in an axial direction; a second rotor core including a substantially disk-shaped second core base and a plurality of secondary claw-shaped magnetic poles formed at equal intervals on an outer peripheral part of the second core base, the secondary claw-shaped magnetic poles protruding radially outward and extending in the axial direction and each secondary claw-shaped magnetic pole being arranged between corresponding primary claw-shaped magnetic poles; and a field member arranged between the first core base and the second core base in the axial direction, wherein, when magnetized in the axial direction, the field member causes the primary claw-shaped magnetic poles to function as primary magnetic poles and the secondary claw-shaped magnetic poles to function as secondary magnetic poles, and auxiliary magnets each of which is arranged in one of a clearance formed by the back surface of one of the claw-shaped magnetic pole and a clearance between one of the primary claw-shaped magnetic poles and the corresponding one of the secondary claw-shaped magnetic poles in a circumferential direction, wherein at least the auxiliary magnets or the field member is formed integrally with at least one of the first rotor core and the second rotor core.
 12. The rotor according to claim 11, wherein the auxiliary magnets include primary back magnets arranged in the clearances formed by the back surfaces of the primary claw-shaped magnetic poles and secondary back magnets arranged in the clearances formed by the back surfaces of the secondary claw-shaped magnetic poles, the primary back magnets are formed integrally with the first rotor core, and the secondary back magnets are formed integrally with the second rotor core.
 13. The rotor according to claim 11, wherein the auxiliary magnets are formed integrally with each rotor core and the field member.
 14. The rotor according to claim 11, wherein the rotor cores are formed by powder magnetic cores.
 15. A motor comprising the rotor according to claim
 11. 